Having resumed 15-10 ahead from the afternoon session, O'Sullivan won three out of the next four frames to join Stephen Hendry (seven), Steve Davis, Ray Reardon ( both six) and John Higgins (four) as multiple winners of the tournament in the modern era.
He hinted that he might follow Hendry into retirement after reaching the final by beating Matthew Stevens in the semis, but plans to continue after a six-month break to spend time with his young son Ronnie Jr, who flanked him as he clasped the trophy for a fourth time that complements his triumphs in 2001, 2004 and 2008.
Asked if he would chase Hendry's record haul of seven, O'Sullivan - who collected the trophy and a cheque for £250,000 - responded: "I'm not going to put a number on it. I'm going to have six months off (to spend time with the family)...it is all good. I will just enjoy the moment.
"A few people doubted me, but I'm not going anywhere."
O'Sullivan, 36, is the oldest winner of the trophy since Dennis Taylor overcame Steve Davis 18-17 in 1985. Taylor was 40 days younger than O'Sullivan when he won his solitary world title. Only his former coach Reardon was an older winner of the tournament when he claimed his sixth world title at the age of 45 in 1978.
He admits he will be forced to consider his options over the next few years if the calendar does not alter after accusing World Snooker chairman Barry Hearn of "blackmailing" players by forcing them to commit to a 50-week tour next year.
O'Sullivan said: "There's a bit more left in the tank, but it's up to certain people to do the right thing and stop trying to blackmail players. I'm not going to hang around for two more years for things to become fair.
"Part of me still wants to play, but I was that ill trying to keep up with the schedule, getting letters from World Snooker, and I'm not prepared to put myself under that stress.
"I know there's a big responsibility to promote the game and I'd play in any tournament if it was physically possible...it's up to the governing body to treat the players right and say they don't expect players to travel to 27 tournaments a year.
"I've had a long time to think about everything, it's not a knee-jerk reaction. I'm not saying I have retired, but family has become the most important thing in my life."
As world champion, O'Sullivan will be seeded second in all of the events next season. His six-month break will have no effect on his ranking.
"It is very hard over 17 days. It is an endurance test...like the iron man. I was able to keep it together over 17 days," said O'Sullivan, who also won the German Masters in February.
"I'd like to congratulate Ali. He had a brilliant tournament. I've come here to entertain in this tournament. That was my main intention."
O'Sullivan paid tribute to sports psychologist Dr Steve Peters for helping him get in the frame of mind for the tournament.
"I wouldn't have been playing if it wasn't for Steve," said O'Sullivan. "I've stuck in there. I've had to face things that I didn't want to face...I have tried to give it a go this season. This just tops it all for me."
Carter conceded that he was beaten by the better man. It was his second defeat to O'Sullivan in a World Championship final after he lost 18-8 to his fellow Essex player in 2008.
"Maybe if he retires, I might win it...who knows," commented Carter, who collected £125,000 for finishing second. "I'm disappointed how I played in the final. When he gets in, he is just a genius. It was great to be in another final, but I'm disappointed to lose. I've come back to play half decent again so I will carry on playing for a bit."
O'Sullivan moved 16-10 clear with a run of 70 in the opening frame of the night. Carter responded with 64 before knocks of 26, 46 and 61 finished matters off. It was a 12th win for O'Sullivan over Carter in their 12th meeting.
Third session report
Ronnie O'Sullivan needs three more frames to claim a fourth world title after constructing a 15-10 lead over Ali Carter in the World Championship final at Sheffield's Crucible Theatre.
Carrying a 10-7 overnight lead into the third session, O'Sullivan began the afternoon on the offensive by progressing to make 101 - his third century of the final and the 70th of the tournament - from a long red in moving 11-7 clear.
Carter's afternoon went from bad to worse when he missed a pink off its spot as O'Sullivan compiled 37 to move 12-7 clear.
Carter was again guilty of squandering chances in falling 13-7 behind before O'Sullivan notched up his fourth straight frame aided by an early 54.
Carter responded with a 41, but missing a mid-range yellow buried Carter's hopes in the 21st frame as O'Sullivan mopped up the colours before blowing a kiss to his son as he headed for a cup of tea at the mid-session interval four frames short of the winning post.
Carter returned to the arena suddenly looking a lot more relaxed and managed to carry off a ragged 22nd frame and raised his arms in jest before an immaculate run of 105 - his highest of the match - saw him win a second straight frame.
With O'Sullivan missing a few balls here and there, Carter rolled in 53 to close the gap to 14-10 before his opponent pieced together 64 to claim the session 5-3 for a 15-10 advantage.
He has won the three mini-sessions of the final 5-3, 5-4 and 5-3 to enable him to boast a five-frame advantage losing only one session in the 17-day marathon - 5-3 to 2010 winner Neil Robertson in the quarter-finals.
They play to a finish from 7.30pm with O'Sullivan chasing three more frames for a title he has previously won in 2001, 2004 and 2008.
Second session report
Ronnie O'Sullivan will carry a 10-7 lead over fellow Englishman Ali Carter into the closing day of the World Championship final at Sheffield's Crucible Theatre.
Having resumed 5-3 adrift from the afternoon session, Carter produced a break of 56 after O'Sullivan missed a red to a middle hole on eight. A poor safety shot later in the frame paved the way for Carter to close to 5-4 behind.
He was first at the table in the 10th frame, but O'Sullivan compiled 49 before a doubled red gave him the initiative to win the frame for a 6-4 advantage as he laid a tough snooker behind the green.
Carter escaped from the snooker, but left the penultimate red for O'Sullivan to polish matters off.
A safety error by Carter in the 11th frame handed O'Sullivan the chance to make 68. Carter slotted a long red, but broke down on 14 by missing an easy red.
O'Sullivan potted a red onto another red hanging over a pocket to put the frame beyond doubt for a 7-4 lead with Carter shaking his head after squandering such an obvious opportunity.
Carter held himself together well to stagger over the line to close to 7-5 behind, but that became 8-5 when Carter missed two blacks off the spot in the 13th frame.
It was clear Carter was struggling with his emotions as much as his game as O'Sullivan got the better of a ragged 14th frame to move 9-5 clear with Carter inadvertently seeing a white and black drop in before conceding needing a snooker.
A break of 59 saw him stop the bleeding by winning the 15th frame, but another missed black off the spot handed O'Sullivan the chance to make a 62 in constructing a 10-6 lead.
Carter looked a bit fatigued but did enough to claim the final frame of the day aided by a fluked red. He faces an uphill battle to win the title when they resume at 2.30pm for the third session on Monday with O'Sullivan chasing eight more frames to clinch his fourth title.
First session report
Ronnie O'Sullivan made two centuries and an immaculate 92 in opening up a 5-3 lead over fellow Englishman Ali Carter in the World Championship final at Sheffield's Crucible Theatre.
Carter lost the 2008 final 18-8 to three-times winner O'Sullivan and noticeably changed his tactics in the opening session of this match as he refused a number of obvious long pots to instead fraternise with a safety approach.
It seemed to work as he split the opening six frames before O'Sullivan's true class came to the fore as he constructed a 92 clearance that he had no right to make before running in a knock of 141 in the eighth frame of the session after slotting an early long red.
The pair resume at 7pm, but there is a real danger that O'Sullivan may prove too strong for Carter, who has yet to beat his opponent in any of their 11 previous meetings.
The first red of the final did not disappear down the hole for over 10 minutes with Carter unfortunate to slot a red after potting a blue to open the pack. O'Sullivan benefited with a 56 helping him move 1-0 ahead.
That became 2-0 when he holed a long red before proceeding to make 117. The warning signs were already there for Carter but with his new mentor, the 2002 world champion Peter Ebdon - who lost in the first round to O'Sullivan - looking on, he refused to depart from his safety strategy.
That seemed to pay dividends as an 84 enabled him to close to 2-1 after O'Sullivan missed a red before Carter restored parity by edging a fairly forgettable fourth frame with a couple of modest contributions.
Carter was first to the punch in the fifth frame, but broke down on 42. O'Sullivan responded with a 52 before his opponent missed green late in the frame to again move ahead by the odd frame in five.
O'Sullivan seemed to push the boat out in the sixth frame as he opted to try to stun a red into a middle bag at pace. The red stayed out as Carter returned to the table to compile a frame-winning knock of 29 after an earlier 25 before he failed to register a ball in the next two frames with O'Sullivan making 141 in around nine minutes to round off the afternoon.
It is obvious to state that Carter will need to make a positive start when they resume for nine more frames in the second session.